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P codepowertrainMedium severity

P20DEExhaust Aftertreatment Fuel Pressure Sensor Circuit

The control module sees an electrical fault in the sensor circuit that measures fuel pressure feeding the exhaust aftertreatment (HC doser) system.

Definition

The PCM uses the exhaust aftertreatment fuel pressure sensor to confirm dosing fuel delivery during DPF regeneration and to protect the doser from over- or under-pressure. P20DE sets as a general circuit fault when the sensor signal is open, shorted, or otherwise implausible without falling neatly into the low or high sub-codes. With the sensor faulted the PCM typically inhibits active regeneration, so soot accumulates in the DPF; the MIL illuminates and continued driving can lead to a derate.

Common causes

  • Failed aftertreatment fuel pressure sensor
  • Chafed or open wiring between the sensor and PCM
  • Corroded, loose, or fuel-contaminated sensor connector
  • Loss of the 5-volt reference or sensor ground
  • PCM input circuit fault (rare)

Common misdiagnoses

  • HC doser injector replaced for what is a sensor wiring fault
  • Fuel supply control valve replaced without circuit testing
  • DPF cleaned or replaced because regens stopped occurring
  • Sensor replaced repeatedly when the harness is chafed to ground

Troubleshooting steps

  1. 1.Read the sensor PID key-on engine-off

    With the system at rest the sensor should report near 0 pressure and a plausible bias voltage (commonly around 0.5 V), not 0.0 V or 5.0 V.

  2. 2.Check the 5-volt reference and ground at the connector

    Back-probe for 4.9-5.1 V on the reference and less than 0.1 V drop on the ground with the key on.

  3. 3.Wiggle-test the harness

    Watch the live PID while flexing the harness along the frame rail and near heat shields; a dropout points to chafed wiring.

  4. 4.Substitute or bench-check the sensor

    Compare sensor output to a mechanical gauge during a commanded dosing event; readings should track within the sensor's tolerance.

  5. 5.Repair wiring or replace the sensor and verify

    Clear the code and run a forced regeneration to confirm pressure reporting is plausible through the whole event.

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